In the prior art, a purely mechanical control technology is used for the placement of an absorption tank in a circuit by mainly two manners. In the first one of the manners, an air path is switched by turning a switch in the air path, and then the absorption tank is detached for the replacement of the absorption tank; and in the other one of the manners, the air path is switched by means of a bypass valve. The air path may be switched directly by a pneumatic switch during a surgery; in some cases, the absorption tank is replaced until the surgery is finished. Due to a manual operation of the switch, the replacement operation is inconvenient.
The first air path control technology for the placement of the absorption tank in the circuit is achieved by a manual reversing valve shown in FIG. 8A. During the normal working conditions, the manual reversing valve is at its position 1, and the air exhaled by a patient flows into the absorption tank; when the absorption tank is required to be replaced, the manual reversing valve is turned to its position 2, and then the air exhaled by the patient directly flows into an absorption circuit without passing through the absorption tank. Due to a manual operation of the switch, a misoperation may be likely caused, that is, it is likely to forget the operation on the manual reversing valve during the removal of the absorption tank, thus causing the temporary open of the air path.
The second air path control technology for the placement of the absorption tank in the circuit is achieved by two spring-return typed two-position three-way valves shown in FIG. 8B. During the normal working conditions, the springs are pressed by the absorption tank and those two two-position three-way valves are at their positions 2, and the air exhaled by a patient flows into the absorption tank; if the absorption tank is required to be replaced, the spring is returned when the absorption tank is removed, and the two-position three-way valves are at their positions 1, and then the air exhaled by the patient flows into an absorption circuit without flowing into the absorption tank. This technology is very demanding for the sealing and coaxiality between two air channel openings of the absorption tank and the two-position three-way valves when the absorption tank is mounted, and poor mounting easily causes an air leakage.